Vol 18, No 5 (2022)

New building materials and products in construction and reconstruction, which improve the performance and efficiency characteristics of buildings, reduce material consumption, cost and labor intensity, are always relevant. A promising direction for further development of composite materials is the employment of pre-bound aggregate materials. Their production is a two-stage process, which involves at first creating an optimal aggregate mix and gluing the grains to each other and secondly filling the voids of the obtained aggregate framework with a high-workability matrix. Presented research is an experimental investigation of physical and technical properties of pre-bound aggregate composite materials. Composites with complex binders are also considered in this study. In such cases, the aggregate framework and the grouting matrix were made of binders of different nature, which are incompatible when the components are mixed ordinarily. When studying composites, a complex of physical and mechanical methods was used. Improvement of physical and mechanical properties of framework composites in comparison with composites obtained according to conventional techno- logy has been established. These advantages are identified primarily for such properties as deformability, impact strength, creep.

The aim of current research was to establish the relationship between the stress state of the ribbed-ring dome framework and the degree of its bracing. It was assumed that the meridional ribs and rings of the dome framework are made of metal. The framework of the dome consists of 24 ribs and 7 rings. The study was performed for a ribbed-ring dome of spherical shape with a span of 39.3 m and a height of 11.0 m on computer models. The initial computer model of the framework of a ribbed-ring dome made of steel I-beams without bracing has been developed. On the basis of the initial model, additional models were developed for the frameworks with bracing between meridional edges in four, eight cyclically symmetric sectors and in all sectors. Both for the initial model and for all models of the dome framework with bracing, computer calculations were performed for the effect of the load from the own weight of the load-bearing and enclosing structures, and two variants of the snow load. During the calculations, deformations, internal forces and stresses in the meridional ribs, upper and intermediate rings of different models were determined, which were compared with each other. Graphs of changes in deformations of the frame, graphs and diagrams of changes in internal forces and stresses in the meridional ribs, in the upper and intermediate rings of the dome, depending on the degree of bracing in the framework, are obtained. An assessment of the influence of bracing on the stress state of the rib-ring dome frame is performed. The peculiarities of the influence of different coupling schemes on the stressed state of the dome frame are noted.

The problem of corrosive destruction of concrete and reinforced concrete structures of industrial buildings affected by aggressive environments does not lose its relevance, because, despite the abundance of modern methods of protection, there are still no radical methods of corrosion control. Corrosive destruction of building materials leads to a strength and load-bearing capacity reduction, loss of aesthetic properties of concrete and reinforced concrete structures and, consequently, to a decrease in the residual life of buildings and structures. The biological factor often acts as an intensifier of corrosive destruction. In this regard, it is reasonable to search for the possibility of predicting the durability of concrete and reinforced concrete structures in aggressive liquid mediums, taking into account the biofactor effect from the standpoint of mass transfer theory. The authors present a model of mass transfer in a concrete structure exposed to aggressive environment and biofouling. The proposed physical and mathematical model considers the properties of concrete and aggressive environment, as well as the kinetics of continuous processes of growth, reproduction and death of microorganisms. The results of numerical experiments on the proposed mathematical model are provided. The application of the received solutions will allow timely monitoring of biocorrosive destruction of concrete and reinforced concrete structures and selecting effective methods of protection.

Geometers have proposed more than 600 analytical surfaces for implementation. The largest number of these surfaces is used in architecture and mechanical engineering. Although digital architecture and free form architecture are now increasingly influencing the design of long-span shell structures and curved buildings, the research and application of analytical surfaces continues on an increasing scale. The purpose of the research is to study the state of affairs in the application of analytical surfaces in the construction and engineering industries and to clarify the classes of surfaces that have found application in the study of physical phenomena or in solving purely mathematical problems, but not used in other areas of human activity. Another goal is to find analytical surfaces promising for application in architecture and mechanical engineering, which are still little known to architects and engineers. It has been established that, as before, designers take new analytical surfaces to implement their creative ideas from well-studied classes of surfaces of revolution, transfer and umbrella, minimal, ruled, wavy surfaces.

The authors present the results of R&D on the topic of coupling slip of threadbar of class Av500P. The aim of the work was to obtain experimental data to study the effect of the threadbar coupling on the slip (deformability) of the joint and taking into account the characteristics of the joint in the design of structures. The strength and deformability of coupling samples of threadbar with a diameter of 16, 25 and 40 mm with an innovative four-sided (four-row) thread profile of class Av500P have been studied in accordance with the methodology of international and Russian standards. The samples were made with different tightening torques of the lock nuts and anchor-adhesive compositions inside the coupling. Along with the results of the study, it can be concluded that these couplings of innovative four-row threadbar of class Av500P meet the requirements of international and Russian standards when applying a certain tightening torque to the tightened lock nuts, depending on the diameter of the fittings to be joined and the use of anchor-adhesive compositions on large and medium diameters of the threadbar to be joined. The diagrams of thread joints obtained during the experiment can be used in design practice when design reinforced concrete structures according to the deformation model. Together, this makes it possible to introduce thread joints into the Russian construction regulatory code.